328 Chapter 12. Model-Based Analysis: The HASARD Method
12.4.3 Analysis of quality features
From the quality model in Figure 12.13, we can derive a number of quality features
of the client-server architecture of websites.
For example, we can derive the contribution factors to a number of quality
attributes. For instance, the navigability of the HTML files depends on the
following factors:
the complexity of the HTML files;
the property of well structured HTML files with reasonable sizes;
the HTML file’s correctness in terms of the hyperlinks are indicative;
the availability of site map;
the availability of the online help system.
Similarly, we can derive that the user gets correct information depending on
the following factors:
the HTML files are correct in terms of the contents are correct;
the data files are correct in terms of their contents are correct;
the server hardware and software do not fail;
the HTML files are up to date, which is updated timely by the server;
the Internet delivers the messages correctly.
The performance of the server depends on the load on the server, which in
turn depends on the following factors:
the number of requests made by the clients;
the server’s computational capability and resources;
the security of the server in sense of the possibility of being attacked by
hackers;
Software Design Methodology 329
the correct behaviour of the Internet in terms of duplicated messages
delivered.
From the quality model, we can also derive the main risks of the architectural
design, which include:
the use of a new format of data file could cause the information not to be
displayed in the client computer;
the compatibility problem of the client code may mean that the system
could not be executed on the client’s computer, and consequently, the
system unusable;
the heavy traffic on the Internet may hinder the usability of the system;
hackers’ attacks may cause the system’s poor performance, and in extreme
cases, the systems clash, information leak, data integrity be damaged when
HTML/Data files are removed or replaced with incorrect ones, etc.
poor indicative hyperlinks may cause bad navigability, which in turn hinder
the user to find required information; etc.
The main trade-off point in the design of a website is the decomposition of
information into HTML files. Too many HTML files may cause a complexity in
the hyperlink network. However, too few HTML files may cause large files to be
transmitted over the Internet and result in poor responsiveness.

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